Last January, Cowen was arrested after more than 10 girls at Perry Upper Elementary School came forward saying the teacher's aid had touched them inappropriately during class.
However, officials believe more children could have been victimized by Cowen.
Students as young as 10 complained Cowen fondled them and touched their breasts, according to arrest affidavits, sometimes during “lengthy hugs and inappropriate touches.”
Assistant Police Chief Forrest Smith said the teacher used his position to take advantage of students.
"He would sit next to them," Smith told the court last May. “He puts his hand on her stomach and then as he continued to talk about the math, he would move his hand up and rub the breast of the child."
Cowen confessed, police said, in interviews at headquarters before he was arrested.
Authorities say they found more than 100 pornographic images and videos of children on Cowen's computer.
Cowen originally pleaded not guilty to the charges against him.
However, on February 22, 2018, he pleaded guilty to all 21 charges against him.
He received 20 years in prison for each count; however, the judge ruled Cowen only has to serve 10 years in prison and the rest of the time against him is suspended.
Kendra Miller, the school's principal, and 5th grade math teacher, Jeffrey Sullins, also face criminal charges after police say they failed to report the accusations.